Dandruff and itchy scalp do not couse hair loss. Patchy baldness (alopecia) doesn't itch. If you scratch hard enough, you can lose some hair, but not permanently, because the follicles are still there.
My suggestions:
1. Stop scratching.
2. Use Nizoral Shampoo 1% (over-the-counter) daily.
3. Sarna lotion (also OTC) can be applied as needed for itch.
Meantime, I advise you to set up a doctor's visit. Investing in one such visit (all it's likely to take) is, I think, worth finding out for sure what you have and making it go away.
Take care.
Dr. Rockoff